A step-down ring for attaching a lens filter to a lens with a diameter of 95mm filter to a lens with a diameter of 105mm.
3.7 inches (95 mm) diameter filters can be installed in situations such as not having a filter that fits large apertures in a standard to medium telephoto range.
Please be aware of vignetting when using a wide angle lens as it uses a lens filter diameter smaller than the diameter of the lens.